1. Field of the Invention
The present invention relates to a welding method, and more specifically, to a welding method that uses a high energy beam such as a laser beam, an electron beam or an ion beam.
2. Description of Related Art
One widely used welding method for joining together a plurality of metallic plates that are stacked on each other is a welding method by laser welding, because it offers advantages such as that there is little processing distortion, high speed welding is possible, and few portions are affected by residual heat.
Japanese Unexamined Patent Application Publication No. 2001-062575 discloses a method of laser welding two metallic plates that are stacked on each other, in which a plurality of nuggets are formed along a closed curve to satisfy the nugget diameter/pitch ≥0.5.
In Japanese Unexamined Patent Application Publication No. 2001-062575, there is a problem that a deformation of an object to be welded occurs due to a heat distortion or a residual stress during a welding process. To address the deformation of the object to be welded during the welding process, a method of carrying out tack welding before carrying out main welding at the tack welded part or a vicinity thereof is known.